Please can someone help me on this? please!

The points 'A' and 'B' are plotted correctly on your graph, so you're
more than halfway to plotting 'C' and 'D'.

You just have to remember what 'x-coordinate' and y-coordinate' mean.

Whenever a point is described with 2 numbers, the first number is the 'x'
and the second number is the 'y'.  You knew that, and that's how you were
able to put 'A' and 'B' in the right places.

Any point:  ( x-coordinate, y-coordinate )

Point 'A': (4, 3) ... x-coordinate is 4, y-coordinate is 3 .
Point 'B': (1, -5)... x-coordinate is 1, y-coordinate is -5 .

Point 'C': 
has the same x-coordinate as 'B' ... it's 1 .
has the same y-coordinate as 'A' ... it's 3 .

So point 'C' is (1, 3).  You should have no trouble marking it on the graph.

An important tip:
When you plot points, you really ought to label them on the graph.
I see the two dots that you put on the graph, but really, the teacher
doesn't know for sure which one you think is 'A' and which one you
think is 'B'.  Later, when you get done plotting 'C' and 'D', you'll have
a real mess on the graph if the points are not labeled.

Answer d; a supplementary angle = 180°, so if that angle = 150°, y would = 30°.